1. Field of the Invention
The present invention relates to a method of fastening flat building boards such as ceramic siding boards to the framework of a building, and to a building board as well as a fixture, which are suited for use in the fastening method.
2. Description of the Related Arts
In an exterior finish work of a building, ceramic siding boards (building boards) are employed for attaching them to the sidewall of a building. For example, in a horizontal board siding work where the building boards are attached to the frame construction with the longitudinal direction of the building boards being directed in the lateral direction (horizontal direction), moisture permeable waterproofing sheets 3 are attached at first to the vertical framework consisting of posts 1 and studs 2, and then, for the purpose of securing a ventilating space, furring strips 4 are attached via the moisture permeable waterproofing sheets 3 to the framework, the positions these furring strips 4 being aligned with the positions of the posts 1 and studs 2 as shown in FIG. 17. Thereafter, building boards (not shown in FIG. 17) are fastened to the furring strips 4 by means of nailing for instance.
On the other hand, in a vertical board siding work where the building boards are attached to the frame construction with the longitudinal direction of the building boards being directed upright (vertical direction), after the moisture permeable waterproofing sheets 3 are attached to the posts 1 and studs 2, furring strips 5 are horizontally attached via the moisture permeable waterproofing sheets 3 to the framework, thereby placing the furring strips 5 at several stages with a predetermined space being secured between each neighboring stages as shown in FIG. 18. In this case, a space S is required to be formed between the furring strips 5 which are disposed side by side in horizontal direction so as to secure a passageway for ventilation.
In the meantime, as an alternative method of fastening building boards to the framework where the aforementioned nailing is not employed, there is known a method of fastening the building boards by making use of a metallic fixture 60 which is exclusively dedicated for the building boards as shown in FIG. 19. This metallic fixture 60 is constructed such that the contacting face portion 61a thereof facing the framework is disposed parallel with and spaced away by a predetermined distance from the supporting face portion 61b thereof for supporting the rear surface of a building board, said predetermined distance being secured by the existence of the connection portion 61c and bent portion 61d of the metallic fixture 60. A mounting portion 62 extending horizontally is projected from the supporting face portion 61b, thereby permitting the shiplap portions of a couple of the neighboring upper and lower building boards 30A and 30B to be fitted therein and engaged with each other, the shiplap portions being formed respectively on the horizontal edge portions 31A and 31B, facing each other, of the neighboring upper and lower building boards 30A and 30B (see also FIG. 20).
When this metallic fixture 60 constructed as mentioned above is employed, it is possible to secure a sufficient ventilating space Sc between the framework and the rear surface of a building board due to the presence of the metallic fixture 60 which has been attached to the furring strips 4. FIG. 20 illustrates a horizontal board siding work of building boards 30 by making use of the metallic fixture 60. Namely, the installation of the building boards 20 can be performed as follows.
First of all, the lowermost building board 30B is horizontally positioned. Then, the upper horizontal edge portion 31B of the lowermost building board 30B is permitted to engage with the underside portion of mounting portion 62 of the metallic fixture 60, thereby positioning the metallic fixture 60. Then, the metallic fixture 60 is fixed, by means of screws or nails 50, to the furring strips 4 or to the posts 1 or studs 2 via the furring strips 4. Then, the lower horizontal edge portion 31A of the next upper building board 30A is permitted to engage with the upper side portion of mounting portion 62 of the metallic fixture 60 that has been fixed in advance, thereby horizontally positioning this upper building board 30A. Then, in the same manner as described above, the upper horizontal edge portion 31B of this building board 30A that has been horizontally positioned is permitted to engage with the underside portion of mounting portion 62 of another metallic fixture 60, and then, this metallic fixture 60 is fixed to the posts 1 or studs 2 by means of screws or nails 50. Thereafter, the same procedures as described above are repeated to attach the building boards 30 horizontally and in multistage to the side of a building, thereby accomplishing a decorative external sidewall.
This fastening method is advantageous in that there is little possibility of damaging the surface of the building boards 30 as seen in the case of the fastening work by way of nailing, and that the existence of the metallic fixture 60 cannot be externally recognized, thus making it possible to provide a fastened state of building boards which is very excellent in external appearance. Further, since a sufficient ventilation space Sc can be secured on the rear side of the building boards 30 that have been fastened to the framework, it is possible to inhibit the generation of dew on the rear surface of the building boards 30.
As described above, in the case of the fastening work of building boards by way of nailing, the nailing is generally limited to only the periphery of a building board, so that unless the nailing is performed strictly following a predetermined specification, it may become difficult to realize a sufficient wind pressure withstanding strength. Additionally, a touch-up coating for the head portion of nail is required to be performed, thus leaving an aesthetic problem.
On the other hand, in the case of the fastening method using the aforementioned metallic fixture, a large number of the furring strips 4 are required to be disposed in order to secure the ventilation space Sc. Therefore, the work load for attaching the furring strips 4 becomes enormous, giving a large influence to the working cost and working period. Additionally, in the case of using the aforementioned metallic fixture, the work for attaching a large number of metallic fixtures to the posts 1 or studs 2 is required.
In the case of a horizontal board siding work, the metallic fixture to be employed is constructed so as to be fitted with the shiplap joint portions (overlying tongue portion and underlying tongue portion) of building boards which are respectively formed on the upper and lower horizontal edge portions of each building board. Therefore, when a large surface load (such as wind pressure) is imposed on the front surface or rear surface of the building boards that have been fastened, the load is required to be endured by the metallic fixtures that have been disposed at the top and bottom sides of a building board. Since each piece of the building boards available in the market at present is relatively small in surface area, the employment of aforementioned metallic fixture for fastening such building boards would not raise any serious inconvenience. However, if the aforementioned conventional metallic fixture is employed for fastening a building board having a much larger surface area which is expected to be placed in the market in near future, it would become difficult to sufficiently endure the load of such a large building board by means of only the metallic fixtures being disposed at the top and bottom side edges of a building board, thus raising a possibility that the fastening portion of metallic fixture would be damaged by a large surface load.